The Institute of Electrical and Electronics Engineers (IEEE) protocol organization has proposed the IEEE1588V2 Precision Time Protocol (PTP), and this protocol may implement time synchronization precision at a sub-microsecond level.
In an internet protocol radio access network (IPRAN), entire-network time synchronization has become an indispensable configuration. Currently, a mainstream entire-network time synchronization solution is an IEEE1588V2 boundary clock (BC) solution, when an IEEE1588V2 BC is used for entire-network time synchronization, clocks in an entire network can be synchronized only with a same time source, multiple time sources cannot coexist, and separate synchronization of multiple clock domains cannot be implemented.
In the IEEE1588 standard, a solution that supports multi-time domains transmission is applying a transparent clock (TC) device. In a TC mode, the TC device supports time transparent transmission, such a scenario may support synchronization of multiple time domains, but TC devices themselves cannot perform time synchronization. As a traversed network, the TC devices themselves lose a capability of time synchronization. Therefore, entire-network time synchronization cannot be implemented.
It can be seen that, as a third-party network, either BC devices in an entire network are selected to perform entire-network time synchronization without support for time transparent transmission, or a TC device is selected to support time transparent transmission without support for entire-network time synchronization. Therefore, a networking scenario is severely limited.
The other approaches cannot implement the scenario, where multiple time domains need to exist in a network, time transparent transmission is required between the time domains, and time synchronization needs to be performed within the multiple time domains.